The broad goals of this proposal are to examine the courses, consequences, and causes of problem and pathological gambling (P&PG) in a sample of 1,200 middle-aged male-male monozygotic and dizygotic twin pair members (2,400 individuals) of the Vietnam Era Twin (VET) Registry. The project has four specific aims: (1) characterize the longitudinal course of P&PG by examining the prevalence and predictors of initiation, progression, persistence, and recovery of P&PG from 1992 to 2001; (2) explore the nosology of P&PG by examining the evidence for a continuity model of P&PG, empirically derived P&PG subtypes, and classic P&PG subtypes described in the P&PG literature; (3) assess the consequences associated 'with P&PG and different P&PG subtypes on health-related quality-of-life, emotional well-being, social adjustment, and socioeconomic status; (4) compare alternate etiological models of P&PG by examining the genetic and environmental overlap in the causes of P&PG with other addictive disorders, disorders of behavioral undercontrol, and disorders of negative affectivity. The twin sample, enriched for individuals at increased risk for developing symptoms of P&PG, has been identified from a cohort of 3,359 twin pairs 'who completed an interview that assessed P&PG in 1992. A broad range of relevant demographic and psychiatric data has already been collected by studies performed in 1987, 1990, and 1992. In the proposed project, a telephone interview will be conducted by the Institute for Survey Research of Temple University to update and expand information about access to gambling, gambling involvement, recent and lifetime symptoms of DSM-III-R and DSM-IV pathological gambling disorder, alcohol abuse and dependence, affective disorders, post-traumatic stress disorder, and antisocial personality disorder. Data will be analyzed using standard epidemiologic (Aim 1), latent class analysis (Aim 2), cotwin-control (Aim 3) and biometrical genetic techniques (Aim 4). Our twin design overcomes a major problem for researchers wishing to perform a population-based study of P&PG by providing a method to efficiently identity individuals who are at increased risk for developing P&PG symptoms. This, combined with the extensive information previously collected from VET Registry members, our large sample size, and the unique analytical flexibility provided by data derived from twins, will permit us to successfully address the project's aims.